Conventionally, piezoelectric ceramic resonators utilizing a basic thickness shear vibration mode have been widely used as resonators in the band of 3.5-12 MHz. Such piezoelectric ceramic resonators utilizing the basic thickness shear vibration mode are disclosed in various documents regarding the related art, such as Patent Document 1.
FIG. 34 is a perspective view showing a conventional piezoelectric ceramic resonator utilizing a fundamental wave of a thickness shear vibration mode.
The piezoelectric ceramic resonator 101 is a so-called strip piezoelectric resonator. Here, a piezoelectric ceramic substrate in a shape of a rectangular plate having a longitudinal direction and a width direction, namely, a strip piezoelectric ceramic substrate 102, is used.
The piezoelectric ceramic substrate 102 is polarized in the longitudinal direction as shown by an illustrated arrow P.
A first excitation electrode 103 is formed on an upper face of the piezoelectric ceramic substrate 102 to extend from a substantial central area to a longitudinal end 102a of the piezoelectric ceramic substrate 102. In addition, the excitation electrode 103 is formed to reach both width-direction ends at the substantial center of the piezoelectric ceramic substrate 102.
A second excitation electrode 104 is formed on a lower face to overlap the excitation electrode 103 at the longitudinal center of the piezoelectric ceramic substrate 102. The second excitation electrode 104 extends from the substantial center of the piezoelectric ceramic substrate 102 toward an end 102b of the piezoelectric ceramic substrate 102.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 10-200364